Aminophenyl-oxazolines



Patented Apr. 19, 193 8 i I i UNITEDMSTATES PATENT OFFICE 2,114,326 amorlmmoxazonmns Roger Adams and Marlin Templeton Leiller, Urbana, Ill., assignors to Abbott Laboratories, North Chicago, 111., a corporation of Illinois No Drawing. Application July 15, 1935, Serial No. 31,454

6 Claims. (Cl. 260-44) Phenyl and various substituted phenyl-2-oxp-amino-m,m-dibromophenyl-2-oxazoline, on the azolines are well-known compounds, but so far other hand, forms salts which hydrolyze in water as we are aware no aminophenyl derivatives of due to decreased basicity of the molecule besuch compounds have ever previously been precause of the two bromine atoms present.

D Salts of the variousbases with hydrochloric We have produced aminophenyl-2-oxazolines acid, hydrobromic acid, sulfuric acid, phosphoric and-substitution products thereof and have disacid, etc., show analogous relationships. With covered that such compounds have value as 10- weak acids, generally an excess of acid is necescal anesthetics. We have found that the comry to increase the solubility substantially over 10 pounds referred to possess local anesthetic acthat of the base. Acids, such as boric, acetic, 10

tivity either by injection or by surface applicaacetamide, etc., may be used. The salts in gention to mucous membranes. These compounds erai show. an acid reaction. are of special value inasmuch as their toxicity The (diethyl and dibutylaminomethyl) 5-(p)- is low in comparison with local anesthetics which aminophenyl-2-oxaxoline forms a mono-hydrohave been commonly employed. The ratio of chloride which is very soluble in water and shows anesthetic efliciency to toxicity in our new coman alkaline reaction. pounds above referred to is a very favorable one, The aminophenyl-2-oxazolines are hydrolyzed and said compoundsare non-irritating in soluby boiling with excess of mineral acid to give tion. Certain of the substitution products dethe hydrochlorides of p-aminoethyl amlnobenon scribed have the unusual property of giving monzoates which with cold alkali are converted to ohydrochlorides which show a basic reaction. p-hydroxyethyl amino-benzamldes.

The compounds to be described may be as- The solutions of the bases or salts in water si ned the general formula: have a local anesthetic action but the solutions m of the salts are more satisfactory since higher concentrations can be obtained. Some of the I I A17 R solid salts are well-crystallized, easily handled o e compounds, and others are hygroscopic. As a Qjl consequence, some of the salt solutions-are most conveniently made by direct titration of the base with an acid without isolation of the salts. In

Where 0116 5B is an amino roup and e other 395 general, excess of mineral acid over the monoare h r n a univalent substitllfmt, Such as basic salt should be avoided as the oxazolines halogen, m h y a d Where are much more susceptible to hydrolysis under and R' are each hydrogen, an alkyl, a Substithese conditions. Excess of weak acids is pertuted alkyl, or an aryl group, or where R and i b1 R" m y f rm t eth r n alicyclic group. The aminophenyl-2-oxazolines are prepared Th min D Y are Somewhat by reduction of the corresponding nitro comsoluble in water. The solubility varies with the pounds by any of th th d commonly used position and nature of substituents present; Th nitro compounds are in general, readily thus, m-amino-phenyi-Z-oxazoline is soluble in formed (1) by condensing the proper nitro or 40 water to the extent of about one per cent at substituted nitro aromatic acid chloride with the 30, and the p-amino-m,m-dibromophenyl2-oxsalt of an amino alkyl halide (produced from azoline is only very slightly soluble. amino ethanol or a substituted amino ethanol with The aminophenyl-2-oxazolines, in general, a halogen acid or phosphorus halide). The inform monobasic salts with strong or weak acids, termediate halogenated amides, thus produced, 45 and he lts. e pecially th wi h rong acids, on treatment with alkali give oxazolines. A secare much more soluble in water than the correond alternative method (2) is to condense the sponding bases. Thus, the monohydrochloride of acid chloride with an amino ethanol, and to p-aminophenyl-2-oxazoiine is soluble in water treat the resulting hydroxy amide with sulfuric at room temperature to over 10 per cent. The acid, thus causing the elimination of water-to 50 form an oxazoline. The third procedure (3) is to treat the hydroxy amide formed in (2) with thionyl chloride in order to replace the hydroxyl with chlorine, which intermediate depending on conditions either loses hydrogen chloride directly or by the action of alkali to give an oxazoline.

The m-aminostyryl Z-oxazoline is best prepared by reduction of the nitro compound with iron in neutral solution.

O-GHR EXAMPLE 1 m-Aminophenyl-Z-oxazoline The corresponding nitro compound may be produced in two ways:

(1) The first method is a slight modification of that previously used by Elfeldt (Ben, 24, 3218 (1891)). To a solution of 20 g. of p-bromoethyl m-nitrobenzamide (prepared as described by Elfeldt or by direct nitration of p-bromoethyl benzamide) in 200 cc. of hot ethyl alcohol at 75 C., an ethyl alcohol solution of 3 g. of sodium hydroxide (aqueous alkali may be used) is added with rapid stirring. After an additional 30 seconds stirring, the reaction mixture is poured into a large volume of cold water. The precipitate is filtered, dissolved in cold 10 per cent hydrochloric acid (below 20 to prevent hydrolysis), filtered again and the solution made alkaline with dilute aqueous ammonia. The crude m-nitrophenyl-Z-oxazoline is recrystallized from 75 per cent ethyl alcohol or ethyl acetate as fine colorless needles, melting point 118-l19.

(2) The second method is by direct nitration of phenyl-Z-oxazoline. To a solution of 3 g. of phenyl-2-oxazo1ine in 12 cc. of concentrated sulfuric acid, cooled to 0, is added, with stirring, 4 cc. of a mixture of equal volumes of concentrated nitric and sulfuric acids. The temperature during nitration should be held between 5-15 C. At the end of twenty minutes, the reaction mixture is poured onto ice and dilute aqueous ammonia added till alkaline. The precipitate is filtered and recrystallized from 75 per cent ethyl alcohol, melting point 118-119.

The amino compound may be made from the nitro compound by any of the common methods of reduction. For example:

(1) A mixture of 1.7 g. of m-nitrophenyl-Z-oxazollne and about 60 g. of clean,.fine iron turnings is well stirred and enough water added to give a thin paste. A few drops of concentrated hydrochloric acid are added and the mixture stirred for about 20 minutes.- After this initial treatment, a few drops of hydrochloric acid, a few grams of iron and, if necessary, a little water are added, from time to time, and the mixture warmed on a steam bath and stirred. About, two

that obtained by the iron reduction; melting point -126 (corrected).

EXAMPLE 2 p-Bromoethyl p-nitrobenzamide A solution of 40 g. of p-nitrobenzoyl chloride in 50 cc. of benzene is added to a solution of 44 g. of fi-bromoethylamine hydrobromide in 200 cc. of water. To this mixture, with vigorous stirring or shaking, a cold 5 per cent solution of 17.8 g. of sodium hydroxide is added in portions, and the reaction mixture kept below 50 C. The crude amide separates soon after the addition of the alkali. The reaction mixture should be alkaline to litmus and should be stirred for two hours to insure removal of any unreacted nitrobenzoyl chloride. The product is recrystallized from benzene, forming fine colorless needles, melting point EXAMPLE 3 p-Amino-m.mdibromophenyl-z-oxazoline Into a solution of 2.5g. of p-aminophenyl-2- oxazoline in 30 cc. of 10 per cent aqueous hydrochloric acid is drawn a slow stream of bromineladen air till the solution takes on a pink tint. The precipitate that forms is filtered and recrystallized from 50 per cent methyl alcohol. It forms short colorless needles, melting point 193-194 (with decomposition).

The structure of this molecule may be proved by suspending in a little alcohol and 30 per cent hydrochloric acid and refluxing till hydrolyzed. The product obtained is 4-amino-3,5-dibromo benzoic acid, melting point 330 (with decomposition), after recrystallization from nitrobenzene.

EXAMPLE 4 Dimethyl-5,5- m) -nitr0phenyl-2oxaz0line The p-hydroxy p methyl n-propyl-m-nitrobenzamide may be prepared as follows:

A solution of 25 g. of m-nitrobenzoyl chloride in 30 cc. of benzene is added to a solution of 12.6

g. of c-methyl-fi-hydroxypropyl amine in 100 cc. of water. To-this emulsion, with vigorous stirring or shaking, is added in portions a cold 5 per cent solution of 5.6 g. of sodium hydroxide. The tem- 5 perature is maintained below 50. The reaction mixture is shaken for two hours to insure the complete removal of any unreacted nitrobenzoyl chloride. The crude fl-methyl-p hydroxypropylm-nitrobenzamide is recrystallized from ethyl l acetate, forming colorless l29l29.5 (corrected).

The nitro oxazoline is formed from the hydroxy amide by ring closure with sulfuric acid.

To 35 g. of fl-methyl-p-hydroxypropyl-m-nitrobenzamide is added with stirring 100 cc. of con centrated sulfuric acid (sp. g. 1.84). The reacplates, melting point tion mixture is warmed slowly to 55", at which. temperature all of the amide should be in solution. Stirring is continued for an additional ten A 20 minutes, at the end of which time the reaction mixture is cooled to 15, poured into 600 g. of

ice-water, filtered from any insoluble material, j and the clear, cold filtrate made. ammoniacal with 10 per cent aqueous ammonia. The precipi colorless needles, melting point 81-82 (corrected).

This compound may be reduced by any of the methods already described to the corresponding amino compound.

EXAMPLE (Dibutylaminomethyl) -5- (p) -nitr0ph.enylz-omazoline The -dibutylamino-;s-hydroxy-n propylp-nitrobenzamide may be produced in the following manner:

A 250 cc. pressure bottle containing 10.0 g. of -cliloro-B-hydroxy -n propyl p -nitrobenzamide (prepared by the method outlined for c-methyl-fihydroxypropyl-m-nitrobcnzamide) and 10.0 g. (two moles) of dibutylamine is heated on the steam-cone for ten to twelve hours, the bottle being shaken at frequent intervals. When the reaction is complete. the cooled pressure bottle is opened, and to the mush of amine hydrochloride and free base is added enough cold per cent hydrochloric acid to make the mixture strongly acidic. Any unreacted amide is removed by extions of ether. The water layer is then cooled to 10, made alkaline with strong sodium hydroxide, and extracted three times with a mixture of {equal portions of benzene and ether. ether-benzene extract over solid potassium hydroxide, the solvents and excess of dibutylamine .are removed by warming under reduced pressure. The residue is dissolved in a small quantity of benzene, and poured into an excess of cold ether.

The crude 'y (dibutylaminomethyl) -,3-hydroxy-.

n-propyl-m-nitrobenzamide is recrystallized from a mixture of benzene and high petroleum ether.- forming yellow spurs, melting point 83.5-84.5

' (corrected).

This product is converted into (dibutylaminomethyl) -5- (p) -nitrophenyl-2-oxazoline by treatment with thionyl chloride.

To 3.5 g.of' -(dibutylaminomethyl) -fl-hydroxyn-propyl-p-nitrobenzamide is added an excess of 33.4 g. cc.) of redistilled thionyl chloride. The amide goes into solution at once with the evolution of heat. The flask containing the reaction mixture is attached to a reflux condenser provided with an eflicient gas-trap and the reaction ice-salt'i bath. to below 59,

1 duringthe neutralization.

$05451 (corrected) tated dimethyl-5,5- (m) -nitrophenyl-2-oxazoline is recrystallized from per cent alcohol, forming oxazoline, andfrom (2). the hydroxy'alkylfnitrobutylaminoinethyU- 5 (p) nitrophenyl -2 -oxa zo-1 amino derivative by the iron-wate ijreduction I I scribed under the preparation of meaminophenyl -.2-oxaz'oline.' tracting the acid solution w1th two 50 cc. porstants is given below:

After drying th mixture refluxed on'a water bath for'one' and one+half to 'two'hours. After thesolution has been cooledto 5, itis pouredinto 175 cc."of dry ether, and allowed to stand at 5;overnight. Thek crystals 'of' dlhydrochloride. wh chjseparatefari filtered,- washed withdry ethr-tbflemove theexcess thionylchloride, anddissolvedln -cello cold water. To the water solution]. cooled in an .is added .slowly {with stirring; a cold concentrated solution; of sodlumli hydroxidei" the temperature being held; below T5 The crude.-. ce*1base usually comes, down as an oil which, ;howver 'soonjsolidifies and is filtered withvsuctionc'L-iThe crude (dibutylaminomethyl -5- (p) nitrophenyh 2+oxazoline is recrystallized from 80' per. centfaiu- .hol,.. forming colorless 'flakes','.:melting point This compound may be reducedjb any methods previously described. to the c inglamino compou'nd. z

Additional aminophenyl oirazolines V -.The. derivatives listed below areprepare'd' y condensation of the proper acid chloridea'ncl e" proper amino alkyl halide o anun aicohoi I give; respectively, the halogenatedalkylljnitr' benzamidefor 'hydroxya'lkyl nitrobenzamida formation of the nitrophenyl or substituted n phenyl'oxazolines from'(1") .thehalogenated IR 1 v v v a,. y benzamides is acco I plished by the method (1 5 scribedunder thepr'e'paration of m-nitropheriyl benzamides is accomplished by (a) the'inethod described under the preparation .of dimethyI-B 51 (m)-nitrophenyl-2-oxazoline, or by (b) A method described under the preparationj ofidiline. The corresponding amino derivativesfare produced by one of the methods of reduction de scribed for m-aminophenyl oxazoline. j

The m-nitrostyryl-2-oxazoline is prepared byf condensation of m-nitrocinnamoyl chloride and": fl-bromoethyl amine to form 5-bromoethyl-mgnitrocinnamamide, which on treatment; withjal kali in the usual manner yields thenitro oxazo line. best reducedxt 'IA-ilist of products made by us J M.P. "o. ,(L oinpouui1 (competed) I o-Jiminophcnyl-2-oxazo- 5 556 Colorless memes I -line. 1 I minmin'oplicnyl-2-oxazo- -126 Colorless needles me. p-lnminophonyl-2-o;azo;- l61 Colorlessgncedlcs Benzene." inc. 1 r lll Amino p mcthoiy 1265-127. 5' (olorless needles ill by l phcn \'l-2-0xazoIinc. v acetate. p Amino nun dihro 193-194 (olorlcss noodles mophcnyl-Z-oxazoline.

Methyl 5 (o) amino 41.5-1'2 Colorlcss platcs. 1 r

phvnyl-Z-oxazolino. 3 1 I 1 Methyl 5 (m) amino ll5-l l6 Colorless needles 1 phenyl-Z-oxnzolinc. 7, g

1 321.1 Methyl 5 (p) amino I28. 5-129. 5 (olorlcss nccrllcs Benzene. I

phcnyl-2-oxazoline. x llimvlhyl 5,5 (In) a 122-123 Colorless prisms E th y l" nminophl-nyl 2- oxazoacetate. 1- linv. I)i1nelhyl 5.5 115-146 (olorlcssneedles Ethyl v uminophcnyl Z-oxuzoacetate. lintv 7 fill Mono-hydrochlorides M. I. C. Crystal- (corrected) 1' mm lizod from A solution of g. of p-aminophenyl-2-oxazoline in dry ether or dry ethyl acetate is treated with Dun-1.11 '1 4,5 (p) 211-212 Colorless nccdlcs E t 11 yl :l m ino phcnyl -2-oxazoacetate. dry hydrogen chloride until precipitation is com- 1110.

(yclohemno 4,5 (p) 155-150 Colorless prisms. E t h yl The product is filtered and purified sevinninophcnyl-l-oxazoacetate. eral times by crystallization from absolute ethyl 1110.

(n)llutyl-1-(p) -1\mino- 107-1015 (olorlcss flakes. Absolute alcohol- S, melting point 254-255 phcnyl 2 oxazolinc alcohol. (with decomposition). Alkali regenerates the (monohydrochloride,). free base lhcnyl 4 (p) amino 150-150. 5 Colorless prisms. E t 11 y l phcgyll-i -oxazolintel 9M 1 C I l Aageti ate In a similar manner, methyl-5-p-aminophenyl- (Dihutyleminomethyh- 204-205 Colorless prisms Absolute non) fi-(m-lamizmp l g ygalcohol By a similar procedure, however, the m-amino- 33535 y :phenyl-2-oxazol1ne forms a dihydrochloride inlkrninostyryl-2-oxezo- 144-145 Yellow needles" EH: {1 which hydrolyzes upon attempts lJO purify. In 8 general, the monohydrochlorides are best made As certain of the amides, which are intermediates in the preparation of the oxazolines derivatives, are new compounds, the constants are given below:

Crystal- M. P. C. Corn und Form lized p0 (corrected) from B-Bromoethyl-o-nitro- 122. 5-123. 5 Colorless Benzene.

benzamide. needles fl-Bromoethyl p nit r0 121-122 Colorless Bcnzcne.

benzamide. needles.

fi-llydroxy-fimethyl n 129-129. 5 Colorless plates. E t h y l prolpyl-ni-nitrobenzeacetate. on e.

fl-Hydroxy-B-metliyl-h- 134. 5-135. 5 Colorless E t b y l proriyl-p-nitrobenzaneedles. acetate. emu E- fi-Chloro-u-plienylethyl- 132. 5-133. 5 Greenish Benzene.

p-nitrohenzemide. needles.

fl-Chioro-n-(mhutyl- 116.5-118 Colorless flakes. Dilute etl'ayl-p-nitro-benzeethanol. ll 6.

fl-Bromoethyl-m-nitro-p- 110-111 Colorless Benzene.

methoxybenzamide. needles.

B-Bromoethyl-m-nitro- 107-108 Colorless Benzene.

cinnamamide. needles.

-Diethy1ainino fi hy 168-164. 5 Colorless spurs. Absolute droxypropyl p -nitroalcohol. beln)zamide (hydrochlo- Dibutylumino-fl-hy- 83. 5- 84. 5 Yellow spurs. Benzene droxypropyl-p-nltroand pebcnzamide. troleum ether. llydroxy-Z-cyclo-hcxyl-p- 210. 5-211. 5 Colorless nee- Ethanol.

nitro-benzam e. dles.

The constants of the intermediate nitro oxazolines which are new compounds are listed below:

M. P. C. Crystal- (ompound (corrected) Form lized from o-Nitrophcny-2-oxazoline. 52-53 Colorless nee- 50% ethdles anol. pNil rophenyl-Z-oxszolino 178-178, 5 Callggless nee- Alcohol. m-Nltro-p-methoxy-phen- 122-12.} Colorless nce- D ilu t o yl-2-oxazoline. es. ethanol. Dimcthyl-5,5 -(m)-Nitro- 81-82 Colorless nee- I) i l u to phcnyl-Z-oxazolinc. es. ethanol. Dimcthyl-5,5-(p)-Nitro- 143-144 Grccnish nce- Dilute phenyl-2-oxezoline. dles. ethanol. Dimcthyl -4,5- (p)-Nitro- 122. 5-123. 5 Colorless nce- D i l u t e phenyl-2-oxazolinc. dies. ethanol. (yclohexsno-4,5- (p) -ni- 129. 5-130. 5 Colorless nee- Absolute trophenyl-Z-oxazolinc. lies. alcohol (n) Butyl-4-(p)-nitropl1cn- 46-47 Light yellow Alcohol yl-2-oxazolinc. needles. Phenyl-4-(p)-Nitrophcn- 108. 5-109 Fine yellow nee- Alcohol yl-2-oxazoline. dies. (Diethylaminomethyl)- 57-5725 Yellow needles" D iluto 5-(p)-nitrophcnyl-2- ethanol. oxazoline. (Dibutylaminomethyh- 60. 5-61 Colorless flakes D l 1 u t e 5-(p)nitrophenyl-2- ethanol. oxszoline. m-Nitrostyryl-2-oxszo- 117-118 Colorless nee- Dilute line. dies. ethanol.

by titration.

To a. solution of 5.0 g. of diethylaminomethyl- 5-(p)-aminophenyl-2-oxazoline in 300 cc. of dry ether is added 27.24 cc. of 0.7433 N absolute alcoholic hydrogen chloride. The mixture is allowed to stand at 5 over night, the hydrochloride filtered, and recrystallized from absolute alcohol. melting point 190-191.

Dibutylaminomethyl-S-(p)-aminophenyl 2 oxaaoline hydrochloride is formed in a similar rzraasnner, giving colorless prisms melting at 204- In like manner, (n) butyl-4-(p) aminophenyl- 2-oxazoline forms a monohydrochloride, colorless flakes; melting point 197-1915".

Similarly, phenyl-4- (p) aminophenyl-2-oxaz0- line gives a monohydrochloride, colorless prisms; melting point 239-240 (with decomposition).

These compounds are anesthetics.

Solutions of aminophenyl-z-ozcazoline salts To a solution of 5.0 g. of m-aminophenyl-2- oxazoline in 100 cc. of methyl alcohol is added 90.72 cc. of 0.3508 N aqueous hydrochloric acid. The water and alcohol arexemoved under diminished pressure and the resulting solid salt made up to desired strength with water. Titration may also be carried out merely by suspending the base 'in aqueous solution.

Similarly, equivalent amounts of hydrobromic acid, sulfuric acid, etc., may be used to obtain the salts desired.

m-Aminophenyl-Z-omcoline solution in acetamide 3. As an anesthetic, dibutylanflnomethyl-S-(p) aminopheny1-2-oxazo1ine monohydrochloride.

4. A compound having the formula:

N-CH:

in which R is an alkyl group. 15 5. As an anesthetic, an aminophenyl-Z-oxazoline.

6. As an anesthetic, a substituted aminophenyl- 2-oxazo1ine having the general formula:

in which R, R, R" and R are selected from 10 the group consisting of hydrogen, alkyl and amino substituted alkyl groups, phenyl groups and radi- 02.15 in which R and R together form an alicyclic group.

ROGER ADAMS. 15 MARLIN TEMPLETON LEFFLER. 

